The cells responsible for immunity are collectively known as immune cells or leukocytes. They are a diverse group of cells that originate from the bone marrow and circulate in the blood and lymphatic system.

Here's a breakdown of the main types of immune cells and their functions:

1. Lymphocytes:

* T lymphocytes (T cells):

* Helper T cells (Th cells): Coordinate the immune response by activating other immune cells.

* Cytotoxic T cells (Tc cells): Directly kill infected or cancerous cells.

* Regulatory T cells (Treg cells): Suppress the immune response to prevent autoimmune reactions.

* B lymphocytes (B cells): Produce antibodies, which bind to and neutralize pathogens.

* Natural killer (NK) cells: Kill infected or cancerous cells without prior sensitization.

2. Myeloid cells:

* Neutrophils: First responders to infection, engulf and destroy bacteria.

* Macrophages: Engulf and destroy pathogens, present antigens to T cells, and secrete cytokines.

* Dendritic cells: Capture antigens and present them to T cells, initiating the adaptive immune response.

* Eosinophils: Fight parasitic infections and allergic reactions.

* Basophils: Release histamine and other inflammatory mediators involved in allergic reactions.

* Mast cells: Located in tissues, release histamine and other inflammatory mediators in response to allergens or pathogens.

3. Other immune cells:

* Platelets: Important for blood clotting and wound healing, can also contribute to inflammation.

* Red blood cells: While not directly involved in immunity, they carry oxygen and can interact with immune cells.

Note: This is a simplified overview. Each type of immune cell has a complex array of functions and interactions with other cells, making the immune system a highly intricate and adaptable network.